Spray a large covered casserole dish with cooking spray and spread 1 can of cream of mushroom soup on the bottom of dish. (best way I’ve found to prevent the potatoes from sticking & adds flavour). Chop onion into very small pieces & set aside. In a separate bowl mix 1 can of cream of mushroom soup, the sour cream and 1 tsp. of soup mix (added for the flavor of the seasonings which makes it extra tasty). Layer potatoes and then spread approx. 6 spoonfulls of soup and sour cream mixture on top, then onions, then ½ cup of cheese.Continue layering and finish with the remaining one cup of cheese for the top. Sprinkle the chives evenly across the top. Bake covered at 300°F for about 1½ hours. Then continue to bake uncovered for approx. another hour or as needed until done and top is slightly browned (test with a fork and make sure the potatoes are done). Note: Baking uncovered at the end helps reduce the excess moisture.